Protostome vs Deutrostomes





  • Protostome = First Mouth


  • Deuterostome = Second Mouth


  • Two groups differ by embryonic development

Deuterostome clade


  • Phylum Echinoderms (Inverts) & phylum Chordata (Vertebrates)
    • Independent evolution of each group


  • Deuterostome = Developmental similarities
    • radial cleavage
    • anus from blastophore


  • HOWEVER: other basal animal phyla share some of these traits
    • Deuterostomes now defined by DNA

Sexual Reproduction in animals results in diploid zygote

Phylum Echinoderms


  • Translates to ‘Spiny Skin’
    • sea stars and urchins
    • slow moving and marine
    • adult = radial, larval = bilateral


  • Thin epidermis covered in hard plates
    • often with bumps or spines

Phylum Echinoderms


  • Translates to ‘Spiny Skin’
    • sea stars and urchins
    • slow moving and marine
    • adult = radial, larval = bilateral


  • Thin epidermis covered in hard plates
    • often with bumps or spines


  • Possess a unique water vascular system
    • flexible hydraulic canals = tube feet

Phylum Chordata (mostly vertebrates)


  • All chordates share 4 traits
  • Some only in embryo stages
  1. Notochord
  2. Dorsal, hollow nerve cord
  3. Pharyngeal slits
  4. Muscular, Post-anal tail


  • 2 invertebrates groups that are more related to vertebrates
    • Cephlachordata (lancelets)
    • Urochordates (tunicates)

Lancelets and Tunicates

Vertebrates are chordates with a backbone




  • Possess skeletal and nervous systems
    • simple to complex backbones
    • lots of unique genes (eg. HOX)



  • Derived trait = neural crest
    • special cells near neural tube in embryo
    • give rise to many vertebrate traits
    • e.g.. teeth, skull cartilage, etc

History of backbones: ~500 million years old


  • Evolved while predators where developing
    • Cambrian period
    • Ocean origins (first 150 mya)


  • Vertebrate: series of bones that make up the vertebral column
    • 57,000 species


  • Vertebrates colonized land 365 mya
  1. Amphibians
  2. Reptiles (w/ birds)
  3. Mammals

Hagfish and Lampreys


  • Only members of vertebrates without jaws
    • sister group


  • Have rudimentary backbones
    • more cartilage than bone


  • Hagfish escape by releasing slime
    • researched to stop bleeding in surgery

Hagfish and Lampreys


  • Only members of vertebrates without jaws
    • sister groups


  • Have rudimentary backbones
    • more cartilage than bone


  • Hagfish escape by releasing slime
    • researched to stop bleeding in surgery


  • Many Lamprey are parasitic on fish
    • invaded Great Lakes

Vertebrates with jaws

Sharks and rays


  • ‘Cartilage fishes’: skeletons mostly cartilage
    • originated 400 mya
    • often with calcium


  • Streamlined body for swift swimming
    • poor maneuverability


  • Birth via eggs or young develop inside mother


  • Modern species diversity shrinking

Ray-finned and Lobe-finned fish








  • Phylogeny: large new vertebrate group with bony endoskeletion
    • fishes = aquatic groups

Ray-finned and Lobe-finned fishes (lung on phylogeny)



  • Important derived traits for fishes:
    • operculum:
    • swim bladder:


  • Ray-finned: bony rays that support fins
    • trout, sea horses, eels


  • Lobe-finned: rod-shaped bone surrounded by muscle in fins
    • lungfish, Coelacanths, tetrapods

Evolution of Tetrapods




  • Fins gradually evolved into limbs
    • Tetrapods colonized land 365 mya
    • move away from fish-like vertebrates



  • Tetrapods derived trait = limbs with digits
    • supports weight
    • digits efficiently support movement

Tiktaalik fossil (aka ‘Fishapod’)







  • New selection of many terrestrial traits
    • head separated from body by a neck
    • add vertebrate to allow head to swing
    • bones of pelvis fuse to backbone
    • many species lost gills (became ears)

Amphibians (frogs and salamanders)


  • Include salamanders, frogs and caecilians

    • 6,000 species

    • caecilians lost legs


  • Rely on skin for gas exchange
    • live in moist habitats


  • Name means ‘dual life’
    • some have aquatic tadpole larvae
    • more related to metamorphosis;
    • gills → legs, lungs, eardrums

Amniotes: tetrapod with terrestrial egg (also rib cage)

Reptiles



  • Lizards, snakes, turtles, crocs and BIRDS
    • many extinct groups
    • small (16mm) to large (12m)


  • Scales with keratin


  • Lay shelled eggs on land


  • Most reptiles are ectothermic

Reptiles



  • Lizards, snakes, turtles, crocs and BIRDS
    • many extinct groups
    • small (16mm) to large (12m)


  • Scales with keratin


  • Lay shelled eggs on land


  • Most reptiles are ectothermic

The origin of birds (members of the reptile family tree)

Mammals


  • Large adaptive radiation post dinosaurs
    • predators, herbivores, flying, aquatic
    • Monotremes = platypus (egg laying)
    • Maruspials = pouched mammals
    • Eutherians = placental mammals


  • Derived Trait: Mammary glands
    • produce milk for offspring
  • Derived Trait: Hair
    • insulation/water saver
  • Derived Trait: Kidney
    • waste removing/water saving organ